Beneficial Effects of Bilateral Subthalamic Stimulation on Non-Motor Symptoms in Parkinson's Disease.

BACKGROUND: STN-DBS is well established to improve motor symptoms and quality of life in patients with PD. While non-motor symptoms are crucial for quality of life in these patients, only neuropsychiatric and neuropsychological symptoms have been systematically studied in a longitudinal design so far. However, these are only a part of the non-motor symptoms spectrum. HYPOTHESIS: We hypothesized that STN-DBS is associated with a beneficial effect on a range of non-motor symptoms. METHODS: In this multicenter, open, prospective, international study (EuroInf-study, UKCRN10084/DRKS00006735) we investigated non-motor effects of STN-DBS in "real-life" use. We evaluated Non-motor Symptom Scale, and Questionnaire, PD Questionnaire-8, Scales for Outcomes of PD motor examination and complications, and activities of daily living preoperatively and at 6 months follow-up in 60 consecutive patients (35 male, mean age: 61.6 ± 7.8 years, mean disease duration: 10.4 ± 4.2 years). RESULTS: All outcomes improved significantly at 6 months follow-up (PD Questionaire-8, p = 0.006; activities of daily living, p = 0.012; all others, p < 0.001; Wilcoxon signed-rank, respectively paired t-test; Bonferroni-correction). Post-hoc analyses of Non-motor Symptom Scale domains showed a significant reduction of sleep/fatigue and miscellaneous domains (p ≤ 0.001), perceptual problems/hallucinations (p = 0.036), and urinary (p = 0.018) scores. Effect sizes were "moderate" for Non-motor Symptom Scale, and motor complications, "large" for motor examination, and "small" for other outcomes. CONCLUSIONS: This study provides evidence that bilateral STN-DBS improves non-motor burden in patients with PD and opens the door to a more balanced evaluation of DBS outcomes. Further randomized studies are needed to confirm these findings and compare DBS non-motor effects to other invasive therapies of advanced PD.

Thalamomuscular coherence in essential tremor: hen or egg in the emergence of tremor?

Thalamomuscular coherence in essential tremor (ET) has consistently been detected in numerous neurophysiological studies. Thereby, spatial properties of coherence indicate a differentiated, somatotopic organization; so far, however, little attention has been paid to temporal aspects of this interdependency. Further insight into the relationship between tremor onset and the onset of coherence could pave the way to more efficient deep brain stimulation (DBS) algorithms for tremor. We studied 10 severely affected ET patients (six females, four males) during surgery for DBS-electrode implantation and simultaneously recorded local field potentials (LFPs) and surface electromyographic signals (EMGs) from the extensor and flexor muscles of the contralateral forearm during its elevation. The temporal relationship between the onset of significant wavelet cross spectrum (WCS) and tremor onset was determined. Moreover, we examined the influence of electrode location within one recording depth on this latency and the coincidence of coherence and tremor for depths with strong overall coherence ("tremor clusters") and those without. Data analysis revealed tremor onset occurring 220 ± 460 ms before the start of significant LFP-EMG coherence. Furthermore, we could detect an anterolateral gradient of WCS onset within one recording depth. Finally, the coincidence of tremor and coherence was significantly higher in tremor clusters. We conclude that tremor onset precedes the beginning of coherence. Besides, within one recording depth there is a spread of the tremor signal. This reflects the importance of somatosensory feedback for ET and questions the suitability of thalamomuscular coherence as a biomarker for "closed-loop" DBS systems to prevent tremor emergence.